The present invention is directed to a sensor for measuring the level of fluid in a vessel, and more particularly, to a sensor for measuring the level of fluid in a vessel by emitting and detecting ultrasonic pulses.
When vessels or tanks are used to contain a fluid, such as water, it is desirable to know the level or height of fluid in the vessel in order to determine the volume of fluid remaining in the vessel. There are many prior art fluid level sensors that determine the level of fluid in a vessel. However, most existing fluid level sensors are xe2x80x9cintrusive,xe2x80x9d which require a sensor to be located inside the vessel. Because the intrusive fluid level sensors are located inside the vessel, the sensors are difficult to mount and may be difficult to access for replacement or repair. Intrusive fluid level sensors are also exposed to the contents of the vessel and pressure inside the vessel, which can be hazardous to the sensor, and the sensor may contaminate the contents of the vessel. Finally, some intrusive fluid level sensors require holes to be drilled in the vessel, which adds additional time and expense to the mounting procedure, and compromises the integrity of the vessel.
Non-intrusive fluid level sensors may be used in place of intrusive fluid level sensors. The non-intrusive fluid level sensors may use a transducer to send ultrasonic pulses through the vessel and detect the reflection of the emitted pulses (an echo pulse) that is generated when the ultrasonic pulses reach a fluid-air (or fluid-gas) interface in the vessel. By measuring the elapsed time between the emission of the original pulse and the detection of the reflected pulse, and knowing the speed of travel of the pulses in the vessel, the level of fluid in the vessel may be determined.
In order to couple the transducer to the walls of the vessel such that the transducer can transmit ultrasonic pulses through wall of the vessel, a couplant must be used. Typically, a xe2x80x9cwetxe2x80x9d couplant, which is a gel or liquid, is used to couple the transducer to the vessel wall. However, wet couplants can be difficult to handle and to contain inside the sensor. Wet couplants increase the difficulty of mounting and replacing a non-intrusive level sensor because the wet couplant may tend to leak or escape when the sensor is unassembled. Furthermore, a wet couplant has a natural tendency to lose moisture, and thus may dehydrate or dry out over time. Accordingly, there is a need for a non-intrusive fluid level sensor which is easy to mount and service, and which reduces the adverse effects associated with the use of wet couplants.
The present invention is a non-intrusive fluid level sensor which utilizes a dry couplant. The fluid level sensor of the present invention is easy to couple to, and decouple from, the vessel, which makes the sensor easy to mount and service. The sensor uses a dry couplant which resists dehydration. In a preferred embodiment, the invention is a sensor for measuring the height of fluid in a vessel, the sensor including a mounting base shaped to be coupled to an exterior surface of a vessel. The sensor further includes a transducer having a pulse source for sending pulses into the vessel and an echo detector for detecting echoes of pulses emitted by the pulse source. The sensor further has a dry couplant located between the transducer and the mounting base, and a processor coupled to said transducer for calculating the height of fluid in said vessel based at least in part upon the time elapsed between the pulses sent by said transducer and echoes detected by said echo detector.
Accordingly, it is the object of the present invention to provide a fluid level sensor that is easy to mount and service, and which resists the adverse effects associated with wet couplants.
Other objects and advantages of the present invention will be apparent from the following description and the accompanying drawings.